The present invention relates to a shifting device for changing a shift position.
A typical vehicle having an automatic transmission has a floor shifting device. A shifting device has a shift lever for switching the gear position of the automatic transmission. Some shifting devices provide manual gear selection as well as automatic gear selection. Such a shifting device typically has a several gates formed in a panel. For example, such a shifting device has a first gate for automatic gear selection, a second gate for manual gear selection, and a third gate for switching between the automatic and manual gear selections.
In the automatic gear selection, a driver moves the shift lever to the first gate and shifts the shift lever to one of a P (parking) position, an R (reverse) position, an N (neutral) position, and a D (advance) position. Accordingly, the gear position of the automatic transmission is changed. In the manual gear selection, the driver moves the shift lever from the first gate to the second gate via the third gate, and selectively moves the shift lever toward M+ position (shift up position) and M− position (shift down position). Accordingly, the gear position of the automatic transmission is manually shifted by one gear at a time.
FIG. 12 is a block diagram of an electrical circuit of a shifting device disclosed in Japanese Laid-Open Patent Publication No. 2002-89676. The shifting device includes a switch main body 51 mounted on a vehicle body. The switch main body 51 has a P contact 52, an R contact 53, an N contact 54, a D contact 55, a shift-up contact 56, and a shift-down contact 57. A negative electrode 58 extends arcuately along the switch main body 51. A shift lever (not shown) has a contact electrode 59, which electrically connects one of the contacts 52 to 57 with the negative electrode 58.
For example, when the shift lever is at the P position, the contact electrode 59 contacts the P contact 52 and the negative electrode 58, thereby electrically connecting the P contact 52 and the negative electrode 58 to each other. Accordingly, a controller 60 determines that the shift lever is at the P position, and switches the gear position of the automatic transmission to the P position. When the shift lever is at any of the R, N, D positions, the controller 60 operates in a similar manner.
When the driver moves the shift lever to the second gate, a position detecting switch (not shown) is turned on. The position detecting switch continues to be on during the manual gear selection. During the manual gear selection, the contact electrode 59 contacts one of the shift-up contact 56 and the shift-down contact 57, and the negative electrode 58. Based on the contacting state of the negative electrode 58 with one of the shift-up and shift-down contacts 56, 57, and an ON signal from the position detecting switch, the controller 60 detects one of a shift-up manipulation and a shift-down manipulation. The controller 60 then changes the gear position of the automatic transmission according to the shift position.
This shifting device is of a contact type, in which the position of the shift lever is detected based on the contact state of the negative electrode 58 with the contacts 52 to 57 with the contact electrode 59. However, if the shifting device is used for an extended period, the contact electrode 59 and the contacts 52 to 59 deteriorate with time due to wear. Therefore, the method using this shifting device has low reliability as a method for detecting the position of the shift lever.